Holland TSTL-3A Coaxial Cable Ringer Toner Tester Tones out cables by inserting a DC current into a coaxial cable at one end and detects that cable from others in a remote location by attaching the audio toning device to the other end.
This is the NEW TSTL-3A Pocket Toner from Holland Electronics... It's longer to accomodate a common AAA 1-1/2 Volt battery instead of the 23A (12 volt) battery. I use this Pocket Toner every day in the Lab, in addition to all the ones we sell, we have only had one return for Failure... And I suspect that was because the User inserted the battery in backwards (you need to pay attention to Polarity with any device). In addition to the Audio Que, the LED lighting up on the Head at the other end can clue you partner that it's time to move to the next cable. I've dropped it plenty o' times without incident. I know guys that have used these for years... and that's why we sell 'em!